This invention relates to an automatic document feeder which is attached to recording appatuses such as electrophtographic copying machines, image reading devices and so forth, and in particular to an automatic document feeder wherein a document sheet on the document platen is transported with a revolving document transport belt pressing it.
Heretofore, in this type of automatic document feeders(Japanese Tokkai-sho 58-38948 etc), as shown in the perspective view of FIG. 7 for example, conveyor belt 1 is an endless belt, which is entrained about a drive roller 2 and an idle roller 3. A pluralty of rows of document pressing rollers are rotatably supported inside the conveyor belt 1. The document pressing rollers, arranged in up-to-downstream direction of the document platen, consist of the first row rollers 4A and 4B, the second row rollers 5A and 5B, and the third row rollers 6A and 6B; each of the document pressing rollers presses the inner side of the conveyor belt 1, which transports the document on the document platen glass plate(platen glass plate), and rotates driven by the conveyor belt.
The document pressing rollers 4A, 5A, and 6A are located at equivalent positions with respect to a direction perpendicular to the document conveyance direction respectively; they press the portions on the same track on the inner surface of the revolving conveyor belt. Also the document pressing rollers 4B, 5B, and 6B are located at equivalent positions with respect to the direction perpendicular to the document conveyance direction respectively, and press the portions on the same track on the inner surface of the revolving conveyor belt. Therefore, these plural rows of document pressing rollers 4A to 6A, 4B to 6B press always the same track portions of the revolving conveyor belt 1, so they have the defect that the track portions pressed by document pressing rollers of the conveyor belt 1 become locally smudged or damaged.